Heat exchanger



R. RIGBY HEAT EXCHANGER Dec. 18, 1,951

5 Sheets-Sheet l Filed July 23. 1947 R. RIGBY HEAT EXCHANGER Dec. 18, 1951 5 Sheets-Sheet 2 Filed July 23, 1947 Fig. 5

Invenror Richard Rlqbg BLLLMZZZM- Dec. 18, 1951 R RlGBY 2,578,945

HEAT EXCHANGER Filed July 23, 1947 5 Sheets-Sheet f5 Ffq. 5

A'Horneq R. RIGBY HEAT EXCHANGER Dec. 18, 1951 5 Sheets-Sheet 5 Filed July 23. 1947 Gal Patented Dec. 18, 1951 l HEAT EXCHANGER mormora Rigby, Great Crosby, Liverpool, mand, assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application July 23, 1947, Serial No. 763,054 In Great Britain May 24, 1946 Section 1, Public Law 690, August 8, 1948 Patent expires May 24, 1966 17 claims. l

This invention relates to heat exchangers of the class comprising heat accumulators adapted to absorb heat from a stream oi relatively warmer uid and to transfer heat to a stream of relatively colder uid, and means operating continuously or intermittently for progressively alternating the exposure of the accumulators to the respective fluids. Heat exchangers of this class are, in this speciiication and claims, designated as accumulator heat exchangers. The heat accumulators in such heat exchangers are usually in the form of a bank of heat-transfer elements having uid passages through the elements from one end of the bank to the other, and such passages are sealed one from another so that different streams of iiuid may pass through different groups of passages simultaneously without being commingled.

Accumulator heat exchangers according to this invention may be used, for example, for preheating air by means of hot waste gas.

Accumulator heat exchangers in common use, such as those of the Ljungstrom or rotating vdrum type, eiect the heating and cooling alternation by the rotation of a suitably partitioned drum containing the heat-transfer elements. When considerable pressure dierences exist between the two gas streams the rotating drum type of heat exchanger presents diillculti'es in sealing, these diiliculties being accentuated with time by the greater wear of the sealing means on the outside of the drum, and the lesser wear of the sealing means about the center.

It is an object of the present invention to provide an accumulator heat exchanger in which the sealing means are .rendered simpler and more effective than in the known types.

A further object is to provide sealing means wherein the pressure on the sealing means is coordinated with the pressure diilerence between the respective huids.

Still another object is to provide an improved accumulator heat exchanger wherein the sealing means is in the form of a closed geometric gure, such as a circle, which sweeps the end face of the bank of heat-transfer elements, such relative motion being eiective either by moving the sealing means over the end of a stationary bank of elements, or by rotating the bank o1' elements while maintaining the sealing means stationary.

According to the present invention, the fluid passages through the accumulator are progressively and alternately exposed to the respective uids by providing shutters which engage the end faces of the heat accumulator along a line or band which surrounds the termini of a selected group of iiuid passages. The two shutters are arranged to sweep, in coordination, the two end faces of the accumulator, each shutter having sealing surfaces separating spaces traversed by the respective uids outside the end faces and providing a variable boundary seal between groups of uid passages selected, as the shutter moves relatively to the accumulator, for registry cf the passages in the accumulator with the respective spaces. It will be understood that such sweeping may be eiecte'd by maintaining either the shutters and seals stationary and rotating the accumulator. or by maintaining the latter xed and rotating the shutters and seals.

Preferably, each shutter has the form of a ring which circumscribes a sealed space maintained in constant communication with an inlet or outlet, as the case may be, of one uid, and also in communication with'a variable selection oi uid passages through the accumulator, the ring being surrounded by a sealed space maintained in constant communication with the outlet or inlet, as the case may be. of the other uid and also in communication with'the variable remainder of the fluid passages through the accumulator. 'I'he iluid passages may be disposed around a longitudinal axis in a bank of heat-transfer elements forming the accumulator. whilst each ring is adapted to sweep an annular end face with a relative movement of revolution of its center about the said axis. When the accumulator is held stationary, the sweeping movement of the shutter ring may be eiected by a rotary drive shaft coaxial with the accumulator through a crank carried by the drive shaft and journalled in the hub o! a spider or similar apertured supporting frame carrying the shutter ring. Alternatively, the transmission from the drive shaft may be through an eccentric keyed to the central shaft and operating within the shutter ring; or the shutter ring may be eccentrically mounted in a rotating ring driven at its periphery by a gear cr the like, thereby obviating the need for a centrai shaft.

'I'he shutter ring may be housed between the end face of the accumulator and a cap at the end o1` the heat exchanger provided with suitable manifolds for the entry and discharge of the fluid streams. The end cap may, accordingly, have an internal face parallel to the end face of the accumulator and may have ports through its center and at the periphery. 'I'he peripheral @ports may be disposed radially or may be turned into an axial direction.

The invention is illustrated by way of example in the accompanying drawings, forming a part of this specification, wherein:

Fig. 1 is a longitudinal sectional view of a heat exchanger according to one embodiment of the invention;

Fig. 2 is a transverse sectional view, taken on line 2-2 of Fig. 1;

Fig. 3 is a transverse sectional view, taken on line 3-3 of Fig. l, showing a modied form of heat-transfer elements in the accumulator;

Fig. 4 is a fragmentary transverse sectional view, similar vto Fig. 3, showing still another modied form of heat-transfer elements;

Fig. 5 is a longitudinal sectional view of another embodiment of the invention;

Fig. 6 is a. transverse sectional view, taken on I, and with the axis of the drive shaft I1. The

heat-transfer elements 2 provide passages 4 through the bank, parallel to the axis or substantially so, from one end face 5a to the other end face 5b. These passages may take any desired form and the heat-transfer elements may be of amr type known per se. The heat-transfer elements may be arranged in partitioned sectors of the bank and may be made of ceramic material but preferably are of metal. The passages may be packed with heat absorbing material in the form, for example, of fine wires, wire mesh, grains, pellets, hollow cylindrical pieces, beads, or rings, or of any other suitable kind. Alternatively, the individual passages may be suitably sized so that their walls constitute an effective and suitably proportioned heat-transfer packing. In the form shown in Fig. 2 the passages are honeycombed, while in the modification shown in Fig. 3 they are formed of radial partitions 2a with corrugated inserts 2b sub-dividing each sector into smaller passages 4a. As shown in Fig. 4, radial partitions 2c with segmental partitions 2d forming passages 4b may also be used.

Shutters 6, in the form of rings, are adapted t sweep the annular end faces a and 5b of the accumulator with a movement of revolution about the axis of the drum. Each shutter ring 6 is housed between an end face, 5a. or 5b, and an end cap, Ia or 1b. Each end cap has an internal face 8 parallel to the end face 5a or 5b of the accumulator and has ports 9 and I2 or I0 and II, through its center and at its periphery for the entry and discharge of the fluid streams.

To insure a snug fit of the shutter 6 with the end face 5a or 5b and the opposing face 8, the shutter is formed of two concentric elements I3 and I4, telescoping together in an axial direction,

the joint between the two parts being rendered gas or fluid tight by means of piston rings I5 or other suitable packing. The radial walls of the elements I3 form sealing faces in engagement with the end face 5a or 5b of the heat accumulator, and the cylindrical portions form sealing walls separating the spaces traversed by the respective fluids, as described hereafter. The two parts I3 and I4 of the shutter may be pre-loaded, i. e., urged apart in the axial direction by means of springs I6, or by other means, so as to provide a small bearing pressure on the sealing face at all times, it beingappreciated that if the pressure inside the ring is greater than the pressure outside of the ring, the bearing pressure will be correspondingly increased by virtue of the pressure of of the fluid inside of the ring tending to urge the rings apart by pressure against the inwardly extending flange of the ring I3.

The sweeping movement of the shutter ring 6 which is in the end cap 'Ia is obtained from a rotary drive shaft I1, journalled in the drum 3 and in a packing I8, in the cap 1b, through a crank I9 carried by the drive shaft and pivoted in the hub 20 of a spider having spokes 2I, carrying the shutter element I4, as shown on the right end of Fig. 1. Alternatively. the transmission from the shaft I1 to the shuter may be through an apertured eccentric element 22, keyed to the shaft, and having rollers 23 for engaging the shutter element I4, as shown at the left end of Fig. 1. The two arrangements may beused in the same heat exchanger, as shown in Figs. 1 to 3, or both ends maybe of the same type of construction.

In operation, each shutter ring E, in its eccentric motion relative to the accumulator, circumscribes a sealed space 24 which is maintained in constant communication with the ports 9 and II) and with a variable selection of fluid passages 4 through the elements 2. Each shutter 6 moves in the sealed space 25 formed between the end face 5a or 5b of the accumulator and the end cap 'Ia or 1b, which space 25 is maintained in constant communication with the ports II and I2 and with the variable remainder of the fluid passages 4.

The fluid which is under relatively higher pressure is passed through the shuter ring 6 and the fluid under relatively lower pressure is passed outside of the shutter. For example, in the recovery of heat from waste gas wherein the waste gas is under a higher pressure than the air tobe heated, the waste gas is introduced through port 9 and discharged through port IIl, whilst the air is introduced through port II and discharged through port I2. The partitioning elements dening the fluid passages 4, and width of the shutter rings will be suchthat the shutter ring will approximately seal and isolate one fluid passage or group of fluid passages from the remainder. It will be understood that, while the countercurrent flow of the gases was described, it is possible to ow them concurrently, by feeding the high pressure gas at Il), the lower pressure gas at I I, and discharging the two gases at 9 and I2, re-

spectively.

The area of the shutter 6 may be made such that it seals 01T approximately half of the annular area ofthe face 5a or 5b between the drums I and 3, whereby the heat-transfer elements of the accumulator are exposed to the two fluids for approximately equal alternating periods. The area may, of course, be varied to attain other ratios between the exposure periods. Each shutter ring 6, being rotatable, effects a creeping rotation about its own axes during the sweeping movement. As a result, over a period of time all points on the sealing faces of the shutters rub against every pointon the corresponding contact face of the accumulator, thereby'effecting a grinding-in action.

In the embodiment according to Figs. 5 and 6 the arrangement of the accumulator and the shutters is similar to that previously described, and like reference numbers indicate like parts. In this embodiment the feed and discharge ports for the low pressure fluid are disposed axially instead of radially to oppose less resistance to the flow of fluid, and the shutters at the opposite ends of the accumulator are driven by separate shafts, thereby obviating the need for sealing means between the shaft and the inner drum 3.

For this purpose, the end caps 1c and 1d are modified to provide axial ports |2a and Ila, respectively, and bearings 26 and 26a are provided to support the shafts |1a and |1b. These shafts are provided with cranks I9 and actuate the shutters '6 as described for the right end of the embodiment according to Fig. l. It will be understood that the shafts 1a and |1b are coordinated by gearsor other means, not shown, to move in synchronism, sealing off the same fluid passages 4 at the opposite ends of the accumulator.

In the embodiment shown in Figs. 'I and 8 the fluid inlet and outlet arrangements are modifled to offer still less resistance to the flow of the fluids, and the accumulator and shutters are modified to provide less dead space within the accumulator drum and to provide for an unequal exposure of the accumulator to the two fluids.

Referring to Fig. 7, 21 is the heat accumulator drum, formed of a metal cylindrical shell rotatably mounted within casing 28 by means of rollers 29, and provided with a peripheral gear rack 30. A spur gear 3|, mounted on a pinion journalled in the casing, engages the gear rack and rotates the drum upon being driven continuously or intermittently by any source of power, not shown. The drum carries heat-transfer elements 32, disposed about the drum axis to provide substantially axial flow passages in the manner previously described for Figs. l to 4. In the form shown in Fig. '1,v however, no central drum is provided.

A pair of ducts 33 and 34 of large diameter are fixed to opposite sides of the casing 28, sealing the latter againstthe outside. outlet ports 35 and 36 permit the inflow and discharge of low pressure fluid.

High pressure ducts 31 and 38 are provided within and eccentric to the ducts 33 and 34 respectively. These ducts have a common axis eccentric to the axis of the accumulator drum, and their ports adjacent to the drum enlarged, as shown at 31a and 38a to provide annular spaces containing shutter rings 39. These rings have their flat faces in engagement with the end faces of the accumulator and are mounted in spiders 4D, supported by means of studs 4| from spiders 42 or similar apertured frames flxed in the ducts 31 and 38. The shutter rings 39 are urged against the end face of the heat accumulator by fluid pressure on the inwardly extending flange of the ring, this sealing action being greater as the pressure difference between the high pressure and the low pressure fluids increases. Springs, as illustrated in Fig. l, may, of course, also be used. Fluid flowing through the ducts Inlet and 31 and 38 is prevented from passing outside of the shutter rings 39 into the ducts 33 and 34 and into that part of the accumulator drum not covered for thetime being by the ducts 31 and 38 by sealing labyrinths 43 or other sealing means. The enlargement at the duct port may be provided with vtwo annular flanges, as shown at 31a, and 31b to provide double labyrinths. The ducts 31 and 38, in the ports of which the sealmg rings 39 are mounted, are each of substantially the same diameter throughout asr the passage through the shutter rings 39; the external diameter of these rings is approximately equal to or slightly greater than half of the diameter of the accumulator drum. This arrangement reduces the amount of unused or dead space within the accumulator drum, whilst insuring that all passages through the drum are adequately swept during the relative movement be-y tween the shutter ring and the accumulator drum during the rotation of the latter.

In operating the heat exchanger according to Fig. 7, the high pressure fluid magy be introduced through the duct 31 and discharged through the duct 38, whilst the low pressure fluid may be flowed c untercurrently, being introduced at 36 and discharged at 35. Concurrent flow is, however, possible by feeding the low pressure fluid at 35 and discharging it at 36. Since the shutter ring 39 has a diameter approximately half of the diameter of the accumulator drum, less than half of the passages through the drum are sealed off by the shutter ring, resulting in unequal exposure of the heattransfer elements to the two fluids.

Referring to Fig. 8, the heat accumulator is mounted in a stationary cylindrical shell 44 having a smaller central drum 45, corresponding to but of smaller diameter than the drum 3 in Fig. 1. The annular space between the drums 44 and 45 isiilled with heat-transfer elements 46 provided with Walls 2 forming axial passages, as described for Figs. l to 4. A pair of stationary ducts 41 and 48 are fixed to the ends of the shell 44, arranged so that their ends remote from the accumulator are curvedaway from the axis of the shell. High pressure stationary ducts 43 and 58 are provided coaxially with the axis of the shell 44, extending through the outer wall of the ducts 41 and 48 in a manner shown in Fig. 7. A pair of rotatable ducts 5I and 52 are connected to the ends of ducts 49 and 50 by means of sealing means at 53 and 53a. At the ends of the rotatable ducts near the accumulator are annular rings 54 and 55 having gear teeth 53 which mesh with spur gears 51. By turning the spur gears in synchronism the ducts 5| and 52 may be rotated to cause their ends nearer the accumulator to sweep the latter.

The ports of the ducts 5| and 52 are enlarged as shown at 5|a and 52a, to provide annular spaces containing shutter rings 58. These rings have their flat faces in engagement with the end faces of the accumulator and are supported by means of spiders 59, studs 60, and perforated supports 6| fixed in the rotatable ducts 5| and 52. Fluid flowing through the ducts 5| and 52 is prevented from passing outside of the shutter rings 58 by sealing labyrinths 62, as in Fig. 7.

The ducts 49, 5U, 5| and 52 are so shaped as to present a minimum obstruction to the flow of fluid. Sweeping of the bank of heat-transfer elements is achieved by applying power to the gears 51, causing rotation of the annular racks or gear rings 54 and 55, and swinging the cranklike ducts Il and 52. For countercurrent flow, the fluid at higher pressure is fed in through duct 49 and discharged through duct 50, whilst the lower pressure fluid is introduced through duct 41 and withdrawn through duct 48. The resulting coaction between the shutter ring and the heat accumulator or bank of heat transfer elements is the same as that for Fig. '7. except that the shutters are moved eccentrically and the heat accumulator is stationary. It will be noted that the internal diameters of the ducts 49, 50, I and 52 are all substantially the same, this being equal to the distance between the drums 44 and 45, whereby the ducts are streamlined for minimum opposition to the flow of the fluid, and the area of the end face of the accumulator bank sealed olf by the'shutter ring is again less than half of the total annular area between these drums.

I claim as my invention:

l. An accumulator heat exchanger comprising: a heat accumulator having a bank of heat-transfer elements mounted in a drum, said drum having a plurality of longitudinal partitions providing a plurality of separate fluid passages, the ends of said partitions terminating in planes at the ends of the drum to form end contact faces; first duct means secured to each end of said accumulator forming a first space for the ilow of a first duid; a shutter at each end of the accumulator within said rst duct means having a flat annular sealing face in engagement with the respective contact face and disposed eccentrically with respect to the drum to surround the termini of a selected partial group of said passages, said sealing face having a width sufficient to span the full cross section at the end of one of said fluid passages, said heat accumulator and shutter being relatively movable so as to effect a coordinated sweeping of said end contact faces by said shutters in engagement with the ends of the partition along a path surrounding the axis of the drum, each shutter having a sealing wall extending from its respective annular sealing face and enclosing a second space for the flow of a second fluid in communication with said selected group of passages and sealed from said first space, said first space being in communication with the fluid passages other than those of said selected group; and secondlduct'means for supplying the second fiuid to the second space at one end of the heat accumulator and for discharging the second fiuid from the second space at the other end of the heat accumulator continuously during relative movement of the heat accumulator and the shutter.

2. A heat exchanger according to claim 1 in which the heat transfer elements are disposed in an annular space between two concentric drums, the said end contact faces of the accumulator being annular.

3. A heat exchanger according to claim 1 in which the heat accumulator is stationary and the shutters are mounted for movement to sweep said end contact faces, and the heat exchanger comprises an axial drive shaft, a crank on the drive shaft, and an apertured supporting frame within a shutter engaged by the crank for imparting said movement to said shutter.

4. A heat exchanger according to claiml in which the heat accumulator is stationary and the shutters are mounted for movement to sweep said end contact faces, and the heat exchanger comprises an axial drive shaft, an apertured eccentric element carried by said drive shaft within a shutter and means connecting said shutter pivotally to said eccentric for rotation about an axis eccentric with respect to said shaft for imparting said movement to said shutter.

5. An accumulator heat exchanger comprising: a heat accumulator having a plurality of longitudinal partitions providing a plurality of separate longitudinal uid passages, the ends of said partitions terminating in planes at the ends of the accumulator to form end contact faces; means for alternately exposing said passages to two fluids comprising a shutter at each of said contact faces mounted for relative motion between the shutters and the accumulator, each shutter having a sealing member with a central opening and a peripheral, flat face extending inwardly from an outer part of the shutter to said central opening for a distance sufficient to cover the full cross section at the end of one of said fluid passages, said flat face being disposed in engagement with the respective contact face of the accumulator surrounding the termini of a selectedfpartial group of said passages to form a variable boundary between said group of passages selected and the passages outside of the sealing member; and means for effecting coordinated relative movement between said accumulator and said shutters for registry of said passages with the respective openings in the sealing members.

6. The heat exchanger according to claim 5 wherein said shutters are mounted for free rotation about their own axes.

7. An accumulator heat exchanger comprising: a heat accumulator having a plurality,of longitudinal partitions disposed to provide a plurality of separate longitudinal fluid passages arranged circumferentially about a longitudinal axis of the accumulator, the ends of said partltio`ns terminating in transverse planes at the ends of the accumulator to form end contact faces; means for alternately.exposing said passages to two fluids comprising a shutter at each of said contact faces mounted for relative motion between the shutters and the accumulator along paths surrounding the said axis, each shutter having a sealing member with a central opening and a peripheral, continuous, at face of substantial width suicient to cover the full cross y A section at the end of one of said fluid passages,

said fiat face being disposed in engagement with the respective contact face of the accumulator' surrounding the termini of a selected partial group of said passages to form a variable boundary between said groups of passages selected and the passages outside of the sealing member, and a peripheral wall extending from said sealing member away from the accumulator and separating spaces traversed by the respective fluids outside the ends of the accumulator; and means for-effecting coordinated relative movement between said accumulator and said shutters for registry of said passages with the' respective spaces.

8. An accumulator heat exchanger according to claim 7 wherein said peripheral wall is joined to said sealing member at the peripherally outer part thereof so as to expose the side of the sealing member away from said fiat face to the pressure of the fluid traversing the space inside the shutter, whereby said sealing member is urged by said pressure against the ends of the partitions.

9. An accumulatorv heatexchanger comprising: a heat accumulator having a plurality of longitudinal partitions providing a plurality of l Q l separatelonsitudinal iiuid es, the ends o said partitions terminating in planes at the ends of the accumulator to form end contact faces; means for -alternately exposing said passages to two fluids comprising a shutter at each' of ysaid contact faces mounted for relative motion between the shutters and the accumulator, each shutter `having a pair. of annular telescoping members at least one of which is a ring, said ring having a ilat face in engagement with the respective contact face'of the accumulator surrounding the termini of a selected partial group of said passages to form. a variable boundary between said groups of passages selected and the passages outside of said ring and means for urging said ring against theI ends of the partitions; and means for effecting coordinated relative movement between the said accumulator and said shutters for registry of said passages with the spaces within the respective rings..

10. The heat exchanger according to claim 9 wherein the means for urging said ring against the ends of the partitions is a spring.

11. The heat exchanger according to claim 9 wherein the means for urging said ring against the ends of the partitions is an annular flange ilxed to the ring and extending inwardly, said flange having a fiat face forming the said ilat raceof the ring in engagement with the ends of the partitions, whereby the side of the flange away from the accumulator is exposed to the pressure of the iluid traversing th space inside the shutter and the ring is urged y said pressure against the ends of the partition.

12. An accumulator heat exchanger comprising: a heat accumulator having a plurality of longitudinal partitions providing a plurality of separate longitudinal uid passages. the ends of said partitions terminating in planes at the ends of the accumulator to form end contact faces; a cap at each end of the heat accumulator having a plane internal face spaced from and parallel to the adjacent end face of the accumulator; a pair of telescoping rings between each end of the accumulator and its respective cap, one of f said rings having an end face engaging the liace of the cap and the other ring having an end face engaging the respective contact face of the accumulator and surrounding the termini of a selected partial group of said passages to form a variable boundary between said groups of passages selected and the passages outside of said ring; a flow passage in each of said caps located to communicate with the space inside the respective pair of rings and forming an inlet or outlet, as the case may be, for the ilow of one iluid through said 4passages selected: duct means at each end of the accumulator for the flow of the other iluid communicating with the space between vthe end of the accumulator and the adiacent cap and outside of said telescoping rings; and means for moving said telescoping rings to sweep the respective contact faces of the accumulator in coordination.

13. In combination with the heat exchanger according to claim l2, means urging the one ring of each telescoping pair against the ends of said partitions and urging the other ring of each pair against said plane face of the cap.

14. An accumulator heat exchanger lcomprising: a heat accumulator having a pair of concentric cylinders and a plurality of longitudinal partitions disposed in the annular space between the cylinders providing a plurality of separate longitudinal Huid passages. the ends of said partitions said cylinders, each shutter having a central opening and a peripheral, substantially circular fiat face in engagement withthe respective contact face and having va 'diameter substantially 'equal to the sum of. the radii of said cylinders and,

positioned so as to extend across the smaller cylinder and beyond on side thereof to the larger cylinder andto surround the terminiv of a selected partial group of said es to form a variable boundary between said groups oi' passages selected and the passages outside of the sealing member; and means for eilecting coordinated relative movement between said accumulator and said shutters for registry of said passages th the respective openings in the sealing mem- 15. An accumulator heat exchanger comprising: a heat accumulator having a plurality of longitudinal partitions providing a plurality of separate longitudinal iluid passages, the ends of said partitions terminating in planes at the ends of the accumulator to form'end contact faces; support means at each contact face mounted for relative motion between the support means and accumulator along a closed path surrounding the axis ofthe drum; means for alternately g exposing said passages to two uids comprising a shutter ring at each of said lcontact faces ro'- tatably mounted on the respective support means eccentrically to said axis, each ring having an outer' diameter less than that of the contact face and a plane annular sealing face in rubbing engagement with the respective contact face of the accumulator surrounding the termini of a selected partial group of said passages to form a variable boundary between said group of passages selected and the, passages outside of the sealing member; and means for e'ecting coordinated relative movement between said accumulator and said support means to move said shutters along vsaidclosed path and into registry with successive partial groups of said passages.

said partitions terminating in planes :at the ends of the accumulator to form end contact faces: a support at each contact face mounted lor relative motion between the support and the accumulator along a closed circular path surrounding the central axis of the accumulator; means for alternately exposing said passages to two fluids comprising a circular shutter ring at each of said contact faces mounted on said supports for free rotation about the respective axes of the shutter rings, said axes of the rings being located eccentrically to said central axis of the drum, each ring having an outer diameter less than that of the contact face and a plane annular sealing face in rubbing engagement with the respective contact face of the accumulator surrounding the termini of a selected partial group,

of said passages to form a variable boundary between said group of passages selected and the passages outside of the sealing member; and means for eiecting coordinated relative movement between said accumulator and said supports to move said shutters along said circular paths and into registry with successive. 9811312151 UNITED STATES PATENTS groups of said 68- Numb'i" Namo Date 1'1. The heat changer www t0 daim 1 '1,933,933 Dow e1 a1. 1 -1.7---- sept. 1s, 1931 wnerem the support comprises an Open frame- 1,s59,573 Riley my 34, 1932 work nxed t0 th Shuttrdd lhft meg bit '5. 1,939,153 vmuuso Dec. 12. 1933 said support an secur sa ramewor a. Y Y. I the msm the shutter ring. FOREIGN PATENTS RICHARD RIGBY. Number Country Date 3 v391,423r Great Britain Feb. 14. 1929 REFERENCES GITED l 19 614,453 Great Britain Dec. 15. 194s The following references are of record 1n the me o! this pgtent: 

